Project Summary The identification of biomarkers for posttraumatic stress disorder (PTSD) has been prioritized as the next crucial step in advancing the assessment, diagnosis, and treatment of PTSD (National Research Action Plan, 2013). Research has identified several genes as promising biomarker candidates for PTSD in adults. Yet, little research has examined genetic associations with PTSD in children, even though children are vulnerable to PTSD. Furthermore, recent evidence suggests that children and adults may have distinct PTSD symptom presentations, which highlights the need for investigating genetic associations with PTSD specifically in a child sample. Identifying genes associated with childhood PTSD would aid efforts to optimize the assessment and diagnosis of PTSD in children. This study would be the first to investigate promising candidate genes for PTSD (SLC6A3, DRD2, TPH2, 5HTR2A, FKBP5, ADCYAP1R1) in school-age children (7-11 years). Furthermore, this study would take the innovative step of examining genetic associations with specific symptoms (e.g., hypervigilance) and symptom clusters (e.g., arousal), which may yield insight into mechanisms through which these genes contribute to PTSD risk and inform future directions for research. Dopaminergic system genes (SLC6A3 and DRD2) are expected to be associated with PTSD symptoms related to arousal. Serotonergic system genes (TPH2 and 5HTR2A) are expected to be associated with symptoms related to alterations in cognitions or mood. Genes associated with hypothalamic-pituitary-adrenal (HPA) axis regulation (FKBP5 and ADCYAP1R1) are expected to be associated with arousal and may be particularly relevant for children, as prior research has found that these genes interact with childhood trauma to predict PTSD in adults; however, no study has examined whether these genes are associated with PTSD in a child sample. The study will also utilize a longitudinal design. Prior longitudinal research has shown that some children recover from PTSD symptoms over time, whereas other children have chronic PTSD. This study will investigate whether genetic associations can predict which children show chronic patterns of distress by examining genetic associations with PTSD symptom severity at two time points (8 months and 15 months postdisaster). Data will be drawn from an ethnically-diverse sample of school-age children exposed to a devastating natural disaster (Hurricane Ike) who provided saliva samples and completed questionnaire measures at two time points. Training will include directed readings, coursework, workshops, conference participation, manuscript preparation, and mentorship via regular face-to-face meetings with experts in childhood PTSD and human genetics. The training received through this NRSA will place the applicant in a position to become a successful independent researcher.